24 MORPHOLOGY AND DEVELOPMENT OF YEASTS 



germination of the zygospore which, in developing, perforate the wall 

 of the asc. The copulation of the asc is always by autogamy and, 

 as each asc contains only four ascospores, it will be able to occur 

 only between sister ascospores. However, by force of circumstances 

 copulation may also be accomplished between ascospores from dif- 

 ferent ascs and consequently from more distant relationships. This 



is almost constantly 



>\ _ -ZZ?S?^^ xJr^CTV^) /^^ ~\.*/^->-^ ~~~4. :l* 



met with when one 

 makes old ascospores 

 germinate; under these 

 circumstances, a great 

 number between them 

 are dead and those 

 which have survived 

 are among others which 



are not capable of de- 

 Fig. 26, Various Stages in the Copulation of the i , ^ 



Ascospores in Swcharomyces Ludwigii. velopment. On account 



of this they will be 



obliged to search in other ascs for ascospores with which to unite. 

 They accomplish their union by means of long organs. 



This copulation is accompanied by numerous parthenogeneses. 

 About one-fourth of the asco- 

 spores germinate without under- 

 going copulation. The analogous 

 phenomenon has been found in 

 Willia Saturnus and in the yeast 

 Johannisberg II (Fig. 27), but 

 for these two species partheno- 

 genesis is still most frequent, 

 and half of the ascospores ger- Fig. 27. Various Stages in the Copulation 

 minate without copulation. of Asc s P res in Yeast Johannisberg II. 



This second form of copulation seems to be quite common among 

 the yeasts. H. Marchand has found this copulation in many yeasts 

 (S. intermedius, turbidans, validus, vini Muntzii, Johannisberg I, 

 S. Willianus). In these yeasts about one-half of the ascospores 

 germinate after having fused two by two; in Saccharomyces validus, 

 however, this copulation is accomplished more rarely and becomes 

 exceptional. Guilliermond has observed the copulation of ascospores 

 in three yeasts reported on and secured from the Chevalier mission 

 (Saccharomyces Mangani, Lindnerii and Chevalieri), and also the 

 yeast from Pulque No. 2. It has been found by Kinokotin in Sac- 

 charomyces paradoxus, but in this yeast it presents very special char- 

 acteristics, the interpretation of which is rather close. Lindner 



